Traditionally, vehicle tires are filled with compressed air. Compressed air when dry consists of about 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases by volume. Water vapor (humidity) can make up as much as 5 percent of the volume of air under worst-case conditions. Nitrogen is becoming a popular replacement for standard air in vehicle tires. When it comes to tire inflation, nitrogen has many advantages over compressed air. With nitrogen tire inflation, improvements can be noted in a vehicle's handling, fuel efficiency and tire life through better tire pressure retention, improved fuel economy and cooler running tire temperatures. See, for example, www.getnitrogen.org.
Filling vehicle tires with nitrogen mainly does two things: it eliminates moisture, and it replaces smaller oxygen molecules with larger nitrogen molecules, reducing the rate at which compressed gas diffuses through porous tire walls. That can mean that a tire filled with nitrogen retains optimal pressure longer, leading to more uniform tire wear and better gas mileage. For example, tires inflated to 32 psi (pounds-per-square inch) get 3 percent better mileage than at 24 psi thus providing fuel economy benefits to drivers. Under-inflated tires are a leading cause of tire blowouts leading to potential accidents and vehicle damage. Nitrogen-inflated tires have been shown to retain pressure longer.
For example, many race car teams use nitrogen instead of compressed air in their tires because nitrogen has a much more consistent rate of expansion and contraction compared to the usual air. A half pound of pressure will radically affect traction and handling. With track and tire temperatures varying over the duration of a race, the consistency of nitrogen is needed.
Nitrogen pressure is more consistent than normal air pressure, because air typically contains varying amounts of moisture due to changes in the relative humidity on race day. Water causes air to be inconsistent in its rate of expansion and contraction. So, a humid race in the southeast United States or a dry race in the desert western United States could make for unpredictable tire pressures if dry nitrogen were not used.
Currently, tire retailers are providing drivers an opportunity to fill up tires with Nitrogen. Ingersoll-Rand Corp. of Montvale, N.J., USA manufactures a Nitrogen Tire Inflation System. However, this system is cost-prohibitive for gasoline stations, convenience stores, cash wash providers, and the like. This system utilizes a semi-permeable membrane to filter nitrogen from ambient air to provide up to 95% pure nitrogen for tire inflation. As such, it is not economical to provide such a system for consumers.
Conventionally, air inflation devices are commonly located at gasoline stations, convenience stores, car washes, and the like. In the past, pay telephones were also located at such locations as well as many other locations. However, pay telephones are being decommissioned with the widespread adoption of cellular telephones. One problem associated with decommissioned pay phones is disposal. What has not been explored in the art is a method of converting decommissioned pay phones to become air or nitrogen inflation devices.
What is needed is a nitrogen tire inflation system which can be located at a gasoline station, convenience store, cash wash provider, and the like which can allow drivers the opportunity to deflate tires filled with compressed air and then inflate with nitrogen.